6K Additive
Frank Roberts walks into bay four, gesticulating at a metal cylinder engulfed in wiring and surrounded by scaffolding. He takes a few steps across the floor and mounts the steps on the right-hand side, all the while detailing the workings of 6K Additive’s UniMelt plasma technology.
The system is currently idle, hence we’re allowed to take a closer look without risk of decontaminating the produce. It is not as big as you might think, nor is the facility as dusty as you might expect. This is the way 6K does things.
“The torch is this very gently moving plume,” the 6K Additive President says of the microwave plasma omitted by the company’s UniMelt technology, “with no violence to it at all. As the particles enter, they’re pretty well behaved as they move down.”
Those particles are moving downwards through the system, but not before they pass through the heat zone where they melt quickly and form a sphere. The length of the plume can be adjusted from 18 inches to eight feet, controlling time and temperature depending on the material being processed. It helps to yield spherical metal powders using less energy than compared to conventional techniques.
6K Additive’s UniMelt process, according to the company, yields metal powders with perfect spherical particles using much less energy. When the company’s staff reference alternative techniques, such as gas atomisation or plasma atomisation, they use words like ‘bash’ and ‘break’, ‘violent’ and ‘aggressive’ to describe how powders are atomised. What you end up with, per Roberts, is ‘broad particle size distribution (PSD), which is resulting in low yield.’ There’s also the issue of powder porosity caused by the ‘aggressive gas flows.’
6K Additive, whose aim is to provide an alternative to such drawbacks, was born off the back of Amastan Technologies acquiring AL Solutions in 2019, with 6K CEO Aaron Bent having led the former and Roberts the founder of the latter. By the following summer, its first two UniMelt systems had been commissioned to process up to 100 tonnes of nickel super alloys and titanium powders each per year. Capacity was doubled in 2021, and when TCT visited the company’s Pittsburgh site in April, work was ongoing to add six more UniMelt systems and commence operations at its prep powder revert evaluation plant down the road.
At this site, an initial sort is carried out before drums of material are XRF scanned to ensure the correct material, and amount of material, is in the container. After this step, a sample is taken for a more comprehensive evaluation, each drum is put through a screening operation, and then loaded onto pails which are transported over to the production facility. 6K is also adding a fleet of five milling machines to the prep site to enable the sizing of
Materials are sized at standard measurements, unless a specific request is made by a customer. The milling process is different depending on the material being used, but nickel will typically be put through a trigger-style mill that uses ball bearing and paddles to ‘mash, flatten and fracture’ the particulate. 6K is prepared to do this at various measurements, whether it’s a standard 15-45μm or a more unconventional 63-75μm.
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“If a customer says they want 63-75μm, well, that’s just a little less sizing for us than if they want 15-45μm,” Roberts explains. “We only put in the reactor what we want to get out of the reactor, that’s what gives us a really high yield proposition. So, you can do some really interesting things. We have customers that are now starting to ask, because they’re looking to enhance their productivity, their parameters, for some strange things like bimodal distribution, because I can maybe optimise my machine and do something a little different with it.”
The only scenario in which 6K steps back from a sizing request is if the market for off-sized powder – say, for an EBM or binder jet process – is saturated to the point that competitors have so much stock they’re selling it for ‘dirt cheap.’ 6K Additive would rather avoid a ‘race to the bottom’ and instead only look to sell off-sized powder (measurements of 45-106μm were used as an example) for higher value metals such as tungsten.
6K Additive’s business model leans on a convergence of economics, sustainability and quality of the product. It won’t leverage the capabilities of its UniMelt if it doesn’t make economic sense to do so, but it won’t hesitate when it does – even if the prospect looks challenging on the surface level.
In its procurement of scrap metal, the company is able to buy feedstock at good value, but unsurprisingly the material isn’t always in the best shape when 6K Additive welcomes it into its facilities. Roberts uses an example of a batch of nickel material that was imported into the facility which had been processed through a system 60 times. It exhibited really high oxygen content and a lot of satellite splatter, but 6K Additive was able to process it with UniMelt after a quick pre-screen to remove any of the 'big splatter'. Out the other side, there was a 60% oxygen reduction in the nickel, while tap density and flow rate were ‘significantly increased.’
“Because you’re consolidating some of these particles, you really tighten the PSD, which is really important,” Roberts explains. “My view is, if additive is going to grow up one day and be mainstream, tightening the PSD and getting one lot to the next all the same [will] enable people to have really robust parameters, that no matter if my powder is the same today as it is two years from now, I get out of ‘well, this lot worked really well and this lot didn’t.’ That’s what they’ve been dealing with a lot with gas atomisers because they can’t control –tightening enough – the output.”
Ensuring high-quality powder is yielded from its UniMelt systems isn’t just a concern within the four operational bays – which are equipped with deflagration vents, flame sensors, and hydrogen detection systems – but also throughout the facility which houses various steps of the process. Roberts outlines that even though manufacturing material is the entire point, he never wants to see any powder around the facility. The company has already received its ISO 9000 quality assurance accreditation and is working on its AS 9100 Quality Management System standard.
With progress to build up the infrastructure and steadily increase its manufacturing capacity here in Pennsylvania moving along nicely, 6K Additive also announced its intentions to expand into Europe – around 50% of the material it currently manufactures is exported to these shores. Last year, François Bonjour was appointed as its European Sales Director, and plans are being drawn up to establish a footprint on the European continent. There are two models being explored. The first is a co-location with super users to ‘create a factory within a factory’ to recycle used powder through on-site UniMelt systems, and the second is to replicate what the company is building in Pittsburgh and deploy a similar site in a centralised location.
“The goal is cost and sustainability,” Roberts sums up. “You need to be close to your customer and it’s convenient for us because they’re also our suppliers. It makes sense to have something here, something there [Europe], [and] at some point, something in Asia. What we’ve been working on over the last year and a half is finalising the blueprint, and then it’s just a matter of where we want to put it. Where’s the most strategic location? By year end, we want full distribution and consolidation at least set up in the EU as there’s a lot of used powder and there’s not an efficient way to get it back here. That’s the next step, we’re working on that pretty aggressively right now.”
